Tractor and trailer

Abstract

An extensible and retractable linear drive ( 5 ) connects a tractor unit ( 1 ) and a trailer unit ( 2 ) and is controlled by a control unit ( 11 ). The progress of the tractor/trailer combination is assisted by alternately forcibly increasing and forcibly decreasing the distance between tractor and trailer units ( 1, 2 ).

What is claimed is:  
     
       1. A tractor/trailer combination comprising 
       a tractor unit and a trailer unit having a distance therebetween,  
       drive means for forcibly increasing and forcibly decreasing the distance between the units, and  
       control means for controlling the drive means so that the distance between the units is automatically repeatedly forcibly increased and forcibly decreased in an alternating cycle at a predetermined frequency.  
     
     
       2. A combination as claimed in claim  1 , in which the drive means comprises an extensible and retractable linear drive connecting the units. 
     
     
       3. A combination as claimed in claim  2 , in which the linear drive comprises a piston-and-cylinder device. 
     
     
       4. A combination as claimed in claim  2 , in which the linear drive is mounted on one of the units and is connected to the other of the units. 
     
     
       5. A combination as claimed in claim  4 , in which said one unit is the trailer unit. 
     
     
       6. A combination as claimed in claim  4 , in which said one unit includes a drawbar connected to said other unit, the linear drive acting on the drawbar to extend and retract it. 
     
     
       7. A combination as claimed in claim  1 , in which the units have land anchors deployable to resist movement of the units in a direction opposite to the direction of travel. 
     
     
       8. A method of assisting the progress of a tractor/trailer combination comprising a tractor unit and a trailer unit having a distance therebetween, the method comprising the step of automatically repeatedly forcibly increasing and forcibly decreasing the distance between the units in an alternating cycle at a predetermined frequency. 
     
     
       9. A method as claimed in claim  8 , including braking the rear unit, with respect to the direction of travel, while the distance between the units is forcibly increased. 
     
     
       10. A method as claimed in claim  8 , including braking the front unit, with respect to the direction of travel, while the distance between the units is forcibly decreased. 
     
     
       11. A method as claimed in claim  8 , including anchoring the units so as to resist movement in a direction opposite to the direction of travel. 
     
     
       12. A method as claimed in claim  8 , in which the cycle of increasing and decreasing distance between the units has a small amplitude relative to the length of each unit. 
     
     
       13. A method as claimed in claim  12 , in which the said cycle has a frequency of at least about one cycle per second. 
     
     
       14. A method as claimed in claim  8 , in which the cycle of increasing and decreasing distance between the units has an amplitude of more than one meter. 
     
     
       15. A method as in claim  8  wherein the distance is increased at a substantially constant speed regardless of amplitude, and the distance is decreased at a substantially constant speed regardless of amplitude, whereby the frequency is inversely proportional to the amplitude. 
     
     
       16. A method as in claim  15  wherein the amplitude is selected by a driver of the truck, whereby said frequency is predetermined.